Review Question - QID 214256

A 68-year-old man is accompanied by his wife to the neurology clinic for “abnormal movements.” The wife reports that the patient appears unstable when walking since he takes short steps when ambulating in his house. His wife reports his right hand has been "shaking" and occurs at rest and improves with purposeful movement. His handwriting has changed recently, where his letters are very small, and he has been having difficulty with clicking his mouse when using the computer. The patient reports that he has been unable to smell food for the past few months and has noticed difficulty with his sleep. He has a medical history of hypertension which is adequately managed with lisinopril. His father had Alzheimer dementia, and his mother passed away “from old age.” Which of the following is the most appropriate method to confirm this patient’s diagnosis?